atw 2018-04v6


atw Vol. 63 (2018) | Issue 4 ı April

| | Fig. 1.

SCWL Coolant Maximum Temperature in LOFA.

| | Fig. 2.

Left: Experimental loop facility THESYS at KALLA showing location where the inter wrapper flow

experiment (see Figure 3) will be installed; right: flow diagram for the IWF tests with four parallel

channels; the valves V2.1-V2.3 control the flow through the assemblies Q1-Q3. V.2.4 controls the

flow in the gap [8].

location where the IWF experiment

will be installed is shown in Figure 2

left. Figure 2 right shows the flow

diagram of the IWF tests with four

parallel channels representing the

three assemblies (Q1-Q3) and the gap

( illustrated by the box containing

Q1-Q3). The flow and temperature

within each assembly and the gap can

be set individually by choosing valve

openings (V2.1-V2.4) and heating

rates according to the KALLA test

matrix. Figure 3 shows the geometry

of the IWF test section.

and mesh resolution for the thermoshydraulic

investigation of the gap and

the bundle. In particular, we include

the upstream components to verify

their influence on the flow field within

the test section. We employ the k-ε

turbulence model and the commercial

CFD-code Star CCM+. Our first

studied case (i) focuses on the gap

| | Fig. 3.

Geometry of the IWF test section, dimensions are in mm, the heated part

of the bundle is marked red on the left side of the figure, 600 mm, [8].

flow and our second case (ii) on the

fuel assembly. For the study of case (i)

a computational domain including

the lower flow distributer, riser pipe

( including venture tube), upper flow

vessel, and the gap are considered (for

corresponding technical drawings of

components refer to Figure 3). For the

study of case (ii) the computational

domain includes the lower flow distributer,

riser pipe (including venture

tube), one inlet expansion and a single

7-pin bundle. Flow properties of the

liquid metal Lead-Bismuth eutectic at

200 °C are employed. Note that corresponding

upstream pipes and flow

conditioners are modelled so that

all relevant geometric details are

captured. Quantifying the effect of

the flow conditioning sections is

important for future simulations, as it

would enable the use of a simpler

computational domain, which still

provides accurate results. In the future

post-test analysis, the smallest representative

computational domain (e.g.,

potentially without flow conditioner

etc.) will be used to compose a fully

coupled thermos-hydraulic simulation

of the three bundles including

the IWF in the gap. Figures 4 left

and right show the computational

domains for the pre-test studies


2 Numerical study

A comprehensive analysis of the

experiment requires efficient simulations.

In the pre-test analysis of the

hydraulics separate simulations of the

gap region and the fuel assembly are

performed. In a first step, we determine

suitable computational domains

| | Fig. 4.

Computational domain for IWF-gap (left) and bundle (right) including the upstream domains.

Operation and New Build

Numerical Analysis of MYRRHA Inter- wrapper Flow Experiment at KALLA ı Abdalla Batta and Andreas G. Class

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